This invention relates to an electric hybrid drive configuration for a front wheel drive vehicle, including a two-mode, input-compound split electromechanical transmission coupled to an internal combustion engine and a pair of electric machines.
A two-mode, input-compound split, electromechanical transmission provides an effective and efficient hybrid drive configuration for medium and heavy weight vehicles. An internal combustion engine and two electric machines are coupled to the transmission, and the machines are independently controlled to either motor or generate depending on the driving condition.
A drive configuration of the above-referenced type is shown and described in the U.S. Pat. No. 5,931,757 to Schmidt, issued on Aug. 3, 1999, and assigned to the assignee of the present invention. In that configuration, three planetary gearsets and both electric machines are coaxially aligned, and the electric machines circumscribe the planetary gearsets. Despite its many advantages, the Schmidt arrangement is not particularly amenable to front wheel drive automotive vehicles, and the circumscribing electric machine configuration tends to complicate design and assembly of the unit. Additionally, the shift point between forward speed modes occurs at non-zero speeds of both machines. Accordingly, what is desired is a two-mode input-compound split electromechanical drive configuration that is better suited to hybrid front wheel drive automotive vehicles, that is less complicated and easier to assemble, and that shifts at or near a zero speed point of at least one of the electric machines.
The present invention is directed to an improved input-compound split hybrid electromechanical drive configuration including a two-mode planetary gearset arrangement coupled to an internal combustion engine and first and second electric machines, wherein the drive configuration includes a transverse output for driving a hybrid front wheel drive vehicle, and the electric machines are disposed on opposite axial ends of the planetary gearset arrangement. A first mode provides reverse, neutral and low speed forward ranges, while a second mode provides a high speed forward range with very high efficiency and low electric power consumption. Shifting between the first and second modes occurs synchronously, and at a zero speed of the second machine, contributing to an exceptionally smooth shift. In the illustrated embodiment, the gearset arrangement includes first, second and third coupled planetary gearsets, with ring of the first gearset coupled to the planet carrier of the third gearset, the first machine coupled to sun gears of each gearset, the second machine coupled to the ring gear of the third gearset, the engine coupled to the planet carrier of the first gearset through an optional input clutch and the output coupled to the planet carrier of the second gearset. A first clutch grounds the ring gear of the second gearset during the first mode, and a second clutch couples the planet carriers of the second and third gearsets during the second mode.